The present invention is classified under international classes H01R and G09F, and relates to an electrified rail, in particularly for metal shelving units which have to be provided, on the side facing the public of the shelves supporting goods, with electronic labels, displays and/or other peripherals. Moreover the present invention relates to the method for producing such electrified rail.
As prior art, the following documents are cited.
Patent application WO 1994/22125 titled “Information display rail system” describes an extruded rail with a C-profile, to be fixed on the front side of the shelves. The rail is provided with a longitudinal top ridge into which an electrically insulating base carrying longitudinally fixed powered wires, opportunely distanced from each other. The wires are fixed with adhesive to said base for about 180° of their section, and protrude downwardly with the remaining free end, with which the spring-loaded ends of an electronic label designed to be fixed into said rail can be brought into contact.
U.S. Pat. No. 5,348,485 titled “Electronic price display system with vertical rail”, also published in 1994, describes a system to connect, through electric wires and plugs, electrified rails positioned on the front of goods-displaying shelves, on which electronic labels are fixed, with a vertical electrified rail, fixed on the uprights of the same shelving unit. The rail is made of an extruded bar inside which electrically conducting metal strips are fixed, with the interposition of an electrically insulating base, the metal strip being fixed through adhesive. The exposed surface of metal strip is touched by flexible spring-loaded electric contacts of end plugs of said connecting wires, said plugs being fixed on said vertical rail, whose electric conductor are connected with their top end to means positioned on the top part of the shelving unit, the means providing supply and control of said electronic labels.
French patent FR 2 765 018 titled “Systeme d'etiquette electronique d'affichage” filed in 1997, describes an electrified rail made of an extruded plastic bar, having a C-profile, on whose bottom is fixed for all its extension an electrically insulating base, on which metal strips are longitudinally fixed through adhesive. Said metal strips are connected with one end to supply and/or control means, while the rail is profiled so as to fix an electronic label having on its rear spring-loaded contacts touching said metal strips, to realize the necessary connection of electronic label with remote supply and control means.
GB patent 1273670 (A) describes a current supply bar comprising an elongate metal support connected by lugs to a wall or ceiling, a flexible strip of insulating material held in the support by flanges, and metal conductors. The strip is provided with grooves into which the conductors are laid when it is flat but which retain the conductors when the strip is bent about its longitudinal axis. The strip is also provided with cavities and/or elevations between the conductors.
U.S. Pat. No. 2,234,745 (A) describes an electric connecting device comprising a rail formed from flexible dielectric material, like for instance rubber. It is provided with a base having flanges whereby the device may be secured in position. Extending through the device and opening at the top edge thereof are two interspaced grooves separated by a centrally arranged ridge. The spacing of the grooves and therefore the width of the ridge is such that the grooves will receive the prongs of a connector. Outer walls are provided on the rail and in the inner face of each of these walls is formed a semi-circular groove in each of which is mounted one of the bus bars made from flexible wire coiled in the form of a helix. When assembling the bus bars in the rail, the bars may be slipped endwise into the grooves while separating the walls slightly so as to allow the bars to be forced down into the grooves until they come opposite the semi-circular grooves, whereupon they will snap into position and will resiliently held in place.
The prior art and all the state of the art known in this technical field have the following limitations:
Referring to the electric conductors of all rails, be they in the form of wires or strips, the part of their surface which is not fixed to support insulating material is visible and easily reachable by a person's fingers, with ensuing safety problems, both for the persons and the electronic labels, whose contacts may be damaged by electrostatic shocks deriving from accidental contacts.
Another disadvantage of the known state of the art is the poor reliability in the fixing of electric conductors to supporting rail through adhesives, whose features tend to modify over time, due to the heating electric conductors undergo because of Joule effect. To remedy this problem, the teaching of U.S. Pat. No. 5,890,918 may be used, which describes how to realize an electrified rail using an extruded body of hard material, also electrically conducing, providing said body with a longitudinal slot with a circular section, outwardly open with a part lower than 180° of its section. In said slot a copper wire is inserted through pressure, the wire being insulated through a sheath of plastic material, having an external diameter equal to the diameter of said slot, so that the same wire can be pressure-inserted and can remain friction-trapped in said slot, which surrounds it for more than 180° of its electrically insulating external sheath. This solution entails the use of pointed pins on plugs and peripherals; the point must be able to pierce wire insulation and to touch the same copper wire to establish the needed electrical contact. This solution entails also very high contact resistances, due to the limited surface contact between pointed pins and conductor wire. Insulation piercing technique needs a strong force to allow the contact point to pierce wire insulation and to touch the wire itself, deforming it to ensure an efficient contact. In U.S. Pat. No. 5,890,918 said force is obtained through a screwable contact in a corresponding seat of the electrified rail. If we consider that every contact must have its own electric insulation and a robust threaded body to ensure a resistant screwing in the electric rail seat, e.g. three or four electric conductors, it is easy to understand that miniaturising the electrified rails and the relative contact plugs becomes very difficult, according to U.S. Pat. No. 5,890,918. Other disadvantages come from the fact that screwable plugs can be subjected to loosening caused by vibrations, with diagnostic and maintenance difficulties. Further disadvantages derive from the fact that every time the peripheral is moved on the electrified rail, other tracts of wire must be pierced, while the previously pierced areas remain exposed, with ensuing problems of electric insulation and oxidation. The same U.S. Pat. No. 5,890,918 patent, as an alternative to the above illustrated solution, teaches to realize the rail with an electrically insulating material, with longitudinal slots with circular section, opened toward the exterior with a part lower than 180° of their section, and inserting into every slot an insulation-free copper wire, having an external diameter equal to that of each slot, so that the wire can be pressure-inserted into the slot, taking advantage of the elasticity of the plastics forming the rail, so that the wire is pressure-trapped in the slot, which surrounds the wire for more than 180° of its section. This solution, if on one hand tries to fix electric wires to the slots of the electrically insulating rail without using adhesives, in reality tackles the problem deriving from the difficulty of keeping the wire in the slot, due to the limited undercut with whom the slot itself holds the wire, which is necessary in order to easily overcome the undercut in the step of insertion of said electric wire into relative slot through thrust. Due to the elasticity of the plastics forming the rail, if the rail is realised with a limited section, small movements of flexion and torsion of the rail itself lead to the wires inevitably coming out from the respective slots. This embodiment, too, is an obstacle for the miniaturisation of an electric rail having a plurality of conductors, and has the above-illustrated problems on the use of plugs with screwable contacts. For these reasons, this solution is hardly feasible at the industrial level, to provide tracts of electrified rail having a length of some meters, already incorporating electric wires in the plastic bar. This solution has the same disadvantages quoted above for document WO 1994/22125, in that the electric wires protrude from their relative support slot for an ample tract of their section, and for this reason can lead to accidental short circuits.
EP Patent 1 233 482 describes the realisation of an electrified bar for use at 220-230 V. In this case, too, the bar is provided with a metal body ensuring mechanical resistance, thermal resistance and linearity; in opposed and flanked positions, longitudinal slots are obtained, the slots being capable of containing plastics extrusions having in their turn deep and narrow longitudinal slots with intermediate, longitudinal and flanked recesses, capable of holding respective electric wires which in this way are sufficiently backed in the respective slots and protected against accidental contacts. This solution does not solve the problem of the miniaturisation of the electrified rail, and does not teach how to realise an electrified rail with a plurality of conductors placed side by side, with an industrial extrusion method, capable of providing bars having a limited section, the desired length and ready to use.
Finally, WO patent 9516293 (A1) describes a conductor rail comprising a bearing structure, an insulator and a conductor or conductors, according to which the bearing structure and the insulating structure of the conductor rail are produced as the same uniform structure by the extrusion method and the conductors are inserted in the rail after extrusion, which allows the bending of the rail under heating or without heating, in any direction, before the insertion of the conductors or after insertion. The conductor rail may be formed from PVC, ABS, Polypropylene, Polyethylene or Polycarbonate, or acrylic resins. No mention is made in this document from the feature that the rail can be flexed fanwise transversally before the insertion of the conductors.